Late blight resistance evaluation using a GFP-tagged P. infestans strain. Leaves were inoculated on plants with GFP-tagged isolate 208m2 and were removed 6 days post inoculation and photographed on a dissecting microscope under a narrow-band GFP filter. (A) Untransformed K41 control. (B) Katahdin. (C) A silenced Rar1-RNAi line (clone 3128). (D) A Sgt1-silenced line (clone 3095). The red circles outline the original location of the 10 μl inoculation drops. Green fluorescence is only observed within the circles in A and C but spreads out of the original inoculation sites in B and D. Bars = 2.5 mm.